Regulation of secretory products of the mouse epididymal epithelium by androgenic steroid hormones will be examined with the use of monoclonal antibodies. These highly specific anitbodies recognize antigenic determinants both on restricted domains of the spermatozoan, and in the epithelial cytoplasm in distinct regions of the epididymis. These antigens may be involved in sperm maturation, since they first appear on the sperm surface in the proximal portions of the epididymal duct. Using monoclonal antibodies as probes, we will investigate the androgen dependence of the epididymal epithelial secretory products, and incorporation of these molecules into the sperm surface. We will then relate thepresence or absence of these molecules into the sperm surface. We will then relate the presence or absence of these sperm surface components with fertilizing capacity of the sperm. These studies should provide important insights into problems of male fertility.